Flow and heat transfer in the air gap behind photovoltaic panels

The impetus of this paper is to analyse numerically and experimentally the flow and heat transfer characteristics of buoyancy-driven air convection behind photovoltaic panels. Both convection and radiation heat exchanges are considered as the heat transfer mechanisms by which the thermal energy is transferred into the air. Numerical and experimental results are obtained for a channel of 7.0 m in height and the channel walls are separated by a distance of 0.23 m. In the experiment heat is supplied to the air gap from heating foil attached to one of the vertical walls. Different input heat fluxes and emissivity of the bounding surfaces are considered in order to show their effect on the heat transfer across the air layer. Detailed studies of the flow and thermal fields in the air are presented in order to explore the thermal behaviour of the air in the channel. Velocity and temperature profiles of the outlet air and the surface temperature of the heated and insulated wall is presented. The numerical results agreed well with the experimental measurements.